First and foremost, do yourself no harm with the cold and flu treatments you choose. Check these dos and don’ts.

Do buy your own nasal spray.If you use someone else’s contaminated bottle, you can introduce bacteria into your nose.

Do keep track of the ingredients in every medicine you’re taking to prevent double dosing.For example, many combination medications contain acetaminophen―so you don’t want to take additional Tylenol, since acetaminophen can be toxic to the liver in high doses. And scores of products, including cough suppressants and medicated cough drops, contain dextromethorphan (DXM). Take more than the recommended dose of DXM and you may feel woozy or experience an irregular heartbeat and temporary high blood pressure.

Don’t use a decongestant nasal spray more than twice a day for three or four days.Overuse can lead to rebound congestion, in which the capillaries of the nose reexpand, causing congestion to return. The rebound effect can require medical treatment.